mountain yellow-legged frogs

Researcher Frank Santana prepares to release his charges into a mountain stream.

The little dotted frogs could not have picked a more picture-perfect day for their release into a remote mountain stream within their historic habitat. As wind rustles the swaying tree crowns and sunshine warms our backs, the team of multi-agency collaborators—along with a bevy of reporters—descends on Indian Creek in the San Jacinto Mountains. Bred at the San Diego Zoo Institute for Conservation Research, 65 juvenile mountain yellow-legged frogs Rana muscosa are stowed in pairs in Tupperware containers (with puncture holes) in 2 large, temperature-controlled coolers, awaiting their freedom…and a feast of fresh crickets skirting over the water’s surface. It’s an exciting milestone, years in the making.

Amphibian Adventure
In 2002, the U.S. Fish and Wildlife Service listed Southern California’s mountain yellow-legged frog (MYLF) as endangered, with fewer than 200 adult frogs scattered throughout perennial streams in the San Gabriel, San Bernardino, and San Jacinto mountains. In 2006, a group of tadpoles (once referred to as pollywogs) were collected from the wild and brought to the Zoo’s Institute for Conservation Research. Research Coordinator Frank Santana took painstaking care of little guys, monitoring tank temperature, water quality, ambient light, and everything that could possibly impact the froglets’ development.

Though there was high survivorship, breeding seemed to be at an impasse, so Frank came up with an experiment to let a subset of the frogs hibernate for 60 days in a wine chiller. This proved to be the answer to the amphibian amour riddle, as the hibernated individuals were soon mating after “waking,” with six clutches of eggs laid within two days. With the fertility issue solved, Frank was able to shift his focus to field reintroduction efforts, which culminated in the dozen people buzzing about the three release sites in the stream on June 12, 2013. By raising the tadpoles in captivity into their tailless juvenile stage (about 14 months), it is hoped that there will be less predation and higher survivorship of these animals in the wild. Driving up to the release site, Frank confides that these dappled frogs are “just as deserving of a CHP escort as the pandas.” Given the years of research and collaboration required to get to this MYLF release, I’d have to agree.

The radio telemetry “backpack” will enable researchers to keep tabs on the mountain yellow-legged frog for 30 days, when it will be removed.

The Fungus Among Us
Mountain yellow-legged frogs have not graced this stream since the 1990s when the perfect storm of habitat loss and degradation, nonnative introduced trout, which eat the frogs and their eggs, and the deadly amphibian chytrid fungus sweeping the globe, conspired to destroy this species. It’s up to humans to repair MYLF habitat and safeguard against the chytrid fungus. As the road wound higher into the mountains, Frank shared with me the “extra step” taken to ensure these animals released have the best chance at survival. “We are soaking the frogs twice for 4 hours in water containing beneficial bacteria, to protect them against the chytrid fungus.” Dr. Vance T. Vredenburg, a professor at San Francisco State University, discovered that a naturally occurring strain of bacteria may help ward off the fungus in frogs. This could be a game changer for amphibian conservation!

Release Me
Frank and Adam Backlin from U.S. Geological Survey (USGS) crouch next to the stream with several Tupperware containers bobbing on the surface. Stream water seeps in through the air holes and the frogs seem giddy with their natural habitat so near. Other USGS staff is testing the tiny “backpacks” of radio transmitters, which will be strapped onto 15 of the frogs released. This will enable researchers to track the frogs for the next 30 days to see where they settle, and then remove the transmitters. Frank wades knee-deep into the creek and gently holds a spotted, two-inch long frog on his palm over the water. The frog pauses (for a photo?), then leaps into the water, diving deep into the blessed muck on the bottom. Frank scoops up another frog. Cameras click. The liberation process is mesmerizing. One frog hops back into his Tupperware, but quickly changes his mind. Splash! As we stand under the warm sun, the frogs begin to swim to the surface, eying their audience from their chilly element. They linger, as we do, savoring this giant leap for amphibian conservation.

THANK YOU! San Diego Zoo Global is grateful to mountain yellow-legged frog recovery collaborators at the Los Angeles Zoo, the U.S. Forest Service, U.S. Geological Survey, California Department of Fish and Game, and U.S. Fish and Wildlife Service.

These mountain yellow-legged froglets will soon be ready for release into the wild.

There is an old saying that it takes a village to raise a child. Well, if it takes a village to rear one Homo sapiens, then it certainly takes a lot of villagers to raise more than 500 mountain yellow-legged frog Rana muscosa tadpoles! In the spring of 2012, four females in our amphibian conservation lab each laid a clutch of eggs. A high level of fertility among the eggs resulted in 500 tadpoles.

Our goal with these animals is to raise them up from the tadpole life stage until metamorphosis. This will give the juvenile frogs a “headstart” that will reduce their vulnerability to predators when they are released into the wild this summer. The upcoming release will be the first time that mountain yellow-legged frogs will have been released into the wild in the frog life stage.

These tadpoles still have some changes to make!

We now have over 300 juvenile froglets housed in our amphibian conservation lab. Housing so many froglets has presented us with many challenges to maintain the excellent environmental and water quality conditions that this sensitive species requires.

Thankfully, we have a great team of researchers and dedicated volunteers here at the San Diego Zoo’s Beckman Center for Conservation Research to help us care for the tadpoles and monitor water-quality levels on a regular basis. San Diego Zoo volunteers are an essential part of ensuring that all our tailed tadpoles can graduate into foraging froglets. With many more tadpoles waiting to undergo metamorphosis, we are looking forward to the day when they have all graduated to the froglet stage so we can release them into the wild.

If you are interested in becoming a volunteer for the San Diego Zoo, check out our volunteer page.

As I step into a stream in the San Jacinto Mountains here in southern California, I am reminded of summers as a child. I can remember my excitement at seeing tadpoles in ponds and rivers, lining up on the banks and warming in the sun’s rays. This summer, I am using my inner child to search for very special tadpoles: the tadpoles of the critically endangered mountain yellow-legged frog.(See post Mountain Yellow-legged Frog Conservation: Life beyond the City.)

We use the tadpoles' distinct spot patterns to identify them in the wild.

We have many questions about the lives of tadpoles in the stream. How many tadpoles are there in a stream in a good year? How far do tadpoles move and how many survive to later stages of development? It is important to know how many tadpoles are surviving into adulthood to properly assess the health and recuperation of these special little locals.

This summer, Frank Santana, a research technician at the San Diego Zoo Institute for Conservation Research, and I have been surveying all of the pools at a stream with a healthy population of mountain yellow-legged frogs. We search for tadpoles in each pool, and we catch as many of those tadpoles as we can. We then take pictures of each little tadpole so that we can, hopefully, re-identify individual tadpoles once we are back in the lab. This summer we have found that we are able to tell individuals apart, because each tadpole has its very own spot pattern! Just like your fingerprints or a zebra’s stripes, each tadpole has unique markings. We also use the spot patterns of adults in the lab to identify them.

Thousands of tadpole photos later, we are confident that we can tell individuals apart. We are using the tadpole data we have collected to conduct a mark-recapture analysis. A tadpole is “marked” the first time it is captured, and then it is matched against tadpoles in future surveys to determine if it has been recaptured.

Adult frogs also have unique patterns that can be used to tell individuals apart.

Mark-recapture analyses allow us to get a better understanding of population dynamics in the wild. For example, we can estimate survival and movement patterns within the stream as well as a total population estimate for the number of tadpoles within the stream. It would be impossible to count every tadpole by sight because they are very hard to detect, but using mark-recapture analysis will help us make a reliable population estimate for the tadpole life stage.

We are very excited to begin our analyses and look forward to sharing our results in order to better understand the ecology of this special local frog species.

Stephanie Wakeling is a summer fellow at the San Diego Zoo Institute for Conservation Research.

While I had seen the frogs in captivity before, seeing them in the wild really blew my mind.

It was our first week out in the field, and we headed up to the San Jacinto Mountains in the San Bernardino National Forest in Southern California to look for mountain yellow-legged frogs (see Frog Blog 2009). Being my first trip as a summer fellow at the San Diego Zoo’s Institute for Conservation Research, the butterflies were driving me crazy; actually, make that ladybugs. Thousands of ladybugs were swarming through the air during the day; I couldn’t even open my mouth without inhaling one.

From left to right: Ron, Frank, Adam, and Liz.

Frank Santana and I arrived at the campground and were greeted by Dr. Ron Swaisgood, head of the Zoo’s Applied Animal Ecology Division, and his family, who were on a camping vacation. Our first task was to join up with U.S. Geological Survey (USGS) biologists Adam and Liz to assess the suitability of frog habitat in a local creek. They led us up a steep trail that made conversation while hiking impossible. However, Adam was unfazed and continued to talk about the local habitat while we listened and sweated. My crying may have made the listening part hard for others, and for that, I apologize.

The views of pine trees and rock formations along the hike almost made it worth it. Once we reached the bottom of the creek, we started a habitat survey. This consists of walking 250 meters (822 feet) at a time and recording the types of plants and substrates seen, as well as a variety of water and air measurements. Conducting these surveys allows us to evaluate the suitability of a creek for mountain yellow-legged frog reintroduction.

Coulter pines have cones the size and weight of a chihauhau and sharp protruding spines.

The stream terrain made for quite an arduous hike, as we waded through cold water, pushed through dense brush, and climbed over HUGE slippery boulders. Only thoughts of mountain yellow-legged frogs and loved ones kept us going. We performed about seven of these transects, crossing waterfalls, bouncing over boulders, and squeezing between tons of trees. During the survey, Dr. Swaisgood pointed out the different species of pine. Jeffrey pines are like a giant scratch-and-sniff sticker, with bark that smells like vanilla. White fir trees have neon green, edible needles in the spring and summer. The needles have a bitter, citrus-y taste at first, which fades into a sweet, minty goodness.

Surveying with the USGS was a lot of fun, and the experience made us realize the amount of dedication and manpower it takes to detect and manage mountain yellow-legged frog populations. Adam surprised us with news that he actually discovered a single female frog in a new location on the mountain earlier in the month. That was encouraging news that the frogs are surviving and, perhaps, spreading. The mountain yellow-legged frog was once plentiful in Southern California and ranged as low as 1,000 feet (300 meters) in elevation. Today there are only 8 known populations (9 with the new population) in Southern California, and they are restricted to high elevation streams above 5,000 feet (1,500 meters).

Once the kids left, we realized how creepy their animal-themed chairs are at night.

After the hike down, it was time for a nap. That night, Dr. Swaisgood and his wife, Janice, cooked us a lovely meal that I slept through, although I hear it was delicious. Dr. S. had a good fire going by the time I got there and the kids went to sleep after dessert (apple cobbler!).

On day two, we enlisted the help of the Swaisgood family to help carry heavy batteries for our frog-loggers used to record frog calls. After a short, but steep, climb, we came to a serene pool between two waterfalls. A small mottled frog was sitting on the bank and jumped into the water as we approached. We scanned the pool for other frogs (two were sitting on the waterfall’s edge) while the first frog swam and rested right next to our feet. Seeing my first mountain yellow-legged frog in the wild inspired this haiku:

As we approach, SPLASH!
Humans have wiped them out, but
It knows…help is here.

Most of the frogs were very tolerant of our presence, letting us get within inches of them before taking flight and jumping into the water.

These tiny little frogs were just beautiful, completely oblivious to their plight. Each of the frogs we stumbled across that day (22 total) got my heart pumping. They all looked very robust and healthy; this gave us hope that the frogs’ populations in Southern California can be restored. The 100+ tadpoles we saw were also a very encouraging sign for the future. On the last day, we said our goodbyes to the Swaisgood family and took off to yet another creek. We drove through some private lands to another known population of mountain yellow-legged frogs in hopes of switching out more batteries. We hope to catch male frogs calling underwater trying to entice females. Unlike most frogs, which use a vocal sac to amplify their calls, the mountain yellow-legged frog lacks vocal sacs and calls mostly underwater. Because sound waves travel faster and farther underwater, the frogs may have evolved this calling behavior for competing with the background noise of the loud creek habitat during periods of high snowmelt.

These batteries are used to power frog-loggers, which are programmed to record underwater audio every half hour for 30 seconds.

But back to the batteries: these ain’t your grandma’s triple As. These are 10-pound motorcycle batteries. These suckers wouldn’t be so bad on their own, but when you throw in the fact that each frog-logger requires three batteries and there are four frog-loggers per stream and only two of us…well, let’s just say that I could often be caught muttering to myself how I was going to crush Frank’s Star Wars collectibles when we got back (Did I mention Frank once compared our field site to the forests of Endor?).

Ron Swaisgood becoming one with the frogs.

On this particular day, the frog-loggers happened to be over a mile away from our truck. Since we could only carry three batteries at a time, we had to make two trips. The first trip was up the creek, which was fairly rugged terrain, but luckily nothing close to the intensity of the first two days. On the way back down (carrying the old batteries back), we found an old fire road that made the hike a bit better, but not much. Some blood, a lot of sweat, and a lot of tears later, we swapped out all the batteries for new ones.

After a long rest and plenty of water later, we had finished our first trip in the field. And I like to think the frogs appreciate the hard work. I know I enjoyed myself. I had a blast meeting some cool new people, seeing some awesome frogs, and enjoying the surrounding wilderness.

James Liu is a summer fellow at the San Diego Zoo’s Institute for Conservation Research.

It has been a while since we last updated readers on the status of the mountain yellow-legged frog Rana muscosa recovery program at the San Diego Zoo’s Institute for Conservation Research (see post, Frog Blog). The long-term goal of the program is to reintroduce the offspring of our managed-care colony back into the wild to supplement the critically endangered Southern California population of mountain yellow-legged frogs.

Frank Santana

Before we get into it too much, let us introduce ourselves. My name is Frank Santana and I am a research technician and graduate student in ecology at SDSU (San Diego State University). Helping me out this summer with the frog research is our summer Fellow, James Liu. James is a fourth-year ecology, behavior, and evolution major at UCLA (University of California, Los Angeles) and currently has one quarter of school remaining as he finishes a minor in conservation biology.

James Liu

Our goal this summer is to get the mountain yellow-legged frog off the federal endangered species list. If that doesn’t pan out, maybe we’ll set more bite-sized goals. Some things we’d REALLY like to accomplish are:

1) Manage our captive population of 65 frogs at the San Diego Zoo’s Beckman Center for Conservation Research and establish a successful captive-breeding program.
2) Work with other zoos to establish populations of mountain yellow-legged frogs in captivity.
3) Conduct field research of the frogs in their natural environment to determine habitat use patterns, observe thermoregulatory behaviors, describe activity patterns, and record frog calls.
4) Determine suitable field sites for future release of captive-bred offspring.

Over the next few months, James and I will chronicle our adventures and discoveries in our quest to save the mountain yellow-legged frog.

Frank Santana is a research technician in the Applied Animal Ecology Division of the San Diego Zoo’s Institute for Conservation Research.
James Liu is a summer fellow at the Institute for Conservation Research.